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cdf_31.c
Go to the documentation of this file.00001 #include "cdflib.h" 00002 void cumgam(double *x,double *a,double *cum,double *ccum) 00003 /* 00004 ********************************************************************** 00005 00006 void cumgam(double *x,double *a,double *cum,double *ccum) 00007 Double precision cUMulative incomplete GAMma distribution 00008 00009 00010 Function 00011 00012 00013 Computes the cumulative of the incomplete gamma 00014 distribution, i.e., the integral from 0 to X of 00015 (1/GAM(A))*EXP(-T)*T**(A-1) DT 00016 where GAM(A) is the complete gamma function of A, i.e., 00017 GAM(A) = integral from 0 to infinity of 00018 EXP(-T)*T**(A-1) DT 00019 00020 00021 Arguments 00022 00023 00024 X --> The upper limit of integration of the incomplete gamma. 00025 X is DOUBLE PRECISION 00026 00027 A --> The shape parameter of the incomplete gamma. 00028 A is DOUBLE PRECISION 00029 00030 CUM <-- Cumulative incomplete gamma distribution. 00031 CUM is DOUBLE PRECISION 00032 00033 CCUM <-- Compliment of Cumulative incomplete gamma distribution. 00034 CCUM is DOUBLE PRECISIO 00035 00036 00037 Method 00038 00039 00040 Calls the routine GRATIO. 00041 00042 ********************************************************************** 00043 */ 00044 { 00045 static int K1 = 0; 00046 /* 00047 .. 00048 .. Executable Statements .. 00049 */ 00050 if(!(*x <= 0.0e0)) goto S10; 00051 *cum = 0.0e0; 00052 *ccum = 1.0e0; 00053 return; 00054 S10: 00055 gratio(a,x,cum,ccum,&K1); 00056 /* 00057 Call gratio routine 00058 */ 00059 return; 00060 } /* END */
